Automatic choke



T. M. BALL ETAL AUTOMAT I C CHOKE July 26, 1966 2 Sheets-Sheet l Filed Aug. 2, 1963 July 26, 1966 T. M. BALL ETAL 3,262,683

AUTOMATIC CHOKE Filed Aug. 2, 1953 2 Sheets-sheet 2 ENTORS 7770 mdsmyd 7l' 0714727 TIC-7727477 United States Patent O 3,262,683 AUTOMATC CHOKE Thomas hi. Ball, Bloomiieid Hills, and Ronald T. Denton, Birmingham, Mich., assigner-s to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Aug. 2, 1963, Ser. No. 299,510 12 Claims. (Cl. 2151-39) This invention relates to improvements in the automatic choke for the carburetor of an internal combustion engine, .and in particular to improved means for modulating the temperature and vacuum actuated means which automatically controls the choke during periods of cold idling and engine warmup.

An object of the invention is to provide a low friction choke control which can be readily adjusted to approximately any desired relationship between engine temperature and the extent of choke opening during all operating conditions of the engine including idling and road load operation.

Another object is to provide such a device which is responsive to engine intake manifold pressure yet which is insensitive to operational variations in such pressure.

Other and more specific objects are to provide such a device cooperable with an unbalanced butteriy type choke blade and with a thermostatic choke control means, which latter yieldingly urges the choke blade closed with increasing force `as the engine temperature decreases. A diaphragm type pressure responsive means having one side of its diaphragm in communication with the inlet manifold or fuel-air induction passage of the carburetor downstream of the throttle valve is provided with an actuating link secured to the diaphragm to shift therewith. The other side of the diaphragm is in communication with latmospheric pressure, so that during operation of the engine at idling or low load conditions, the diaphragm and link will shift to a limit of movement referred to herein as :an actuated position.

A movement limiting slot provided in the actuating link extends parallel to the direction of movement of the diaphragm and link to the actuated position and contains one end of a second link having its other end connected to a crank arm of the choke blade shaft to open the choke blade in accordance with movement of the diaphragm toward the actuated position. The movement limiting slot is dimensioned so that upon movement of the diaphragm and first named link to the actuated position when the'engine is cold and opening of the choke blade is resisted by the temperature responsive means, said one end of the second link will bottom against one end of the slot and be pulled to open the choke blade at least to a minimum cold idling or kick position.

in order to increase the choke opening as increasing engine temperature relaxes the temperature responsive force urging the choke blade to its closed position, a modulating coil spring is connected under tension between the tirst and second links to urge said one end of the second link in a choke opening movement until said one end bottoms against the other end of the movement limiting slot. By suitably determining the tension in the coil spring, the length of the movement limiting slot, and the closing force exerted by the temperature responsive means, any desired relationship between the extent of the choke opening and engine temperature can be approximated.

ln the above regard, the two links are arranged substantially in linear alignment with each other and with the movement limiting slot which extends perpendicularly to the diaphragm. The coil spring is also stretched with its axis in alignment with the slot. By this arrangement, frictional interaction is minimized, especially any 3,262,683 Patented July 25, 1966 scissors-type frictional engagement or bearing load which would otherwise hinder the usefulness of the device in consequence of the comparatively small actuating forces involved.

The size of the diaphragm is determined in accordance with the choke closing force of the temperature responsive means to shift the diaphragm and first link to the actuated position whenever the manifold pressure downstream of the throttle valve falls a predetermined amount below the manifold pressure which normally exists during engine cranking. This latter condition is essential in order to prevent pulsating opening of the choke blade during cranking. After the engine is started,

the manifold pressure will be at a minimum during idling and will cause the diaphragm to snap immediately to the Aactuated position in opposition to the temperature responsive means regardless of the engine temperature. As .the engine load increases toward wide open throttle conditions, the manifold pressure will rise so that the manifold vacuum alone may notv be suicient to hold the choke open to the kick position. By this time, however, the increased air flow in the induction passage impinging on the unbalanced choke blade will add sufcient choke opening force to overcome the temperature responsive means and maintain the choke open at least to the kick position. Thus once the engine starts, the choke will remain open at least to the kick position, regardless of the ambient temperature.

The spring modulation described enables elimination of the piston type pressure Vresponsive choke actuator and the substitution of the more economical and trouble free diaphragm type actuator. Heretofore this piston type actuator, which was subject to severe frictional problems and tended to become gummed by the residue of fuel vapors was required because it was susceptible of staged porting, whereby various choke positions could be readily obtained with different conditions of engine load and temperature. Such conditions :are now readily obtained by the spring modulated diaphragm type choke actuating device described herein.

Another object is to form the second link of comparatively heavy rigid wire stock and to provide an open loop or U-shaped bend therein preferably at a location between its attachment with the crank arm and modulating spring, where such a spring is employed. By suitably increasing or decreasing the opening of the loop, the extent of choke opening at the kick position can be readily adjusted. Thus means are readily provided for 'accommodating the numerous tolerances in the linkage and for effecting a nal preferred setting for the choke blade at the kick position.

The structure described including the U-shaped bend in the wire link is desirable to provide simple means for adjusting the extent of choke opening at the kick position if some other arrangement of the modulating spring is employed, or even if no modulating spring is employed.

Other objects of this invention will appear in the following description and appended claims, reference being had to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

FIGURE l is a plan view of a carburetor embodying the present invention.

FIGURE 2 is a graph showing the relationship between the choke blade angle and temperature during engine idling conditions.

FIGURE 3 is an isometric view of the vacuum actuated device and connecting Alinkage embodying the present invention.

FIGURE 4 is a side elevational view taken in the direction of the arrow 4 of FIGURE l.

FIGURE 5 is a fragmentary sectional view taken in 3 the direction of the arrows along the line 5 5 of FIG- URE 1.

FIGURE 6 is a View showing the relationship between the thermostat and vacuum pressure operated device and the choke shaft, taken in the direction of the arrows Substantially along the line 6 6` of FIGURE 1.

FIGURE 7 is a sectional view taken substantially in the direction of the arrows along the line 7-7 of FIG- URE 6.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts il-lustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

Referring to the drawings a particular embodiment of the present invention is illustrated by way of example in a carburetor 10 having a vertical induction conduit 11 which opens upwardly to receive combustion supporting air. Fuel is admixed with the air in the carburetor in accordance with conventional practice and discharged at the lower or throttle end..

The upper end of the carburetor provides the usual air horn ring 12 for attachment with an air iilter. Slightly below the ring 12 is a horizontally extending unbalenced Ichoke blade or valve 13 secured by screws 14a to a choke shaft 14 journalled in the body of the carburetor 10 at opposite sides of the induction conduit or passage 11. As illustrated in FIGURES 1 and 4, the shaft 14 is oiset slightly from the diameter of the passage 11, so that a major portion of the choke blade 13 will be leftward of the shaft 14 in FIGURE 1. In consequence, the unbalanced choke blade 13 is susceptible of being blown to an open position by the air ow through the passage 11 when the engine is under load or cruising conditions. Referring to FIGURE 5, the throttle valve 15 is mounted on a pivotal shaft 16 journalled in the carburetor body at opposite sides of the passage 11 and is actuated by a manually operated throttle lever 17 to control the fuel-air flow in the passage 11 tothe engine.

' wise from the cam surface 23 in FIGURE 4 is a series of radially inwardly stepped arcuate cam surfaces 23a. An adjustable cam fol-lower screw 24 extends radially toward the cam surfaces 2.3 and 23a to ride therealong upon pivoting of the cam lever 22 and is supported by a swinging arm 25 pivoted on an extension of throttle shaft 16. Integral with the lever 25 is a stop portion Z6 which engages a mating stop 27 integral with the throttle lever 17. Thus upon counter-clockwise or closing movement of throttle lever 17, its stop 27 Vwill engage stop 26 to swing the latter and lever 25 counter-clockwise. Then if the engine is operating below a predetermined temperature, follower 24 will engage the appropriate sur- -face of the c-am portions 23, 23a to limit Vclosing of the throttle blade 15 at a corresponding fast idle position. Also integral with throttle lever 17 is yan unloader lever 2S engageable uponclockwise or opening movement of throttle valve 15 in FIGURE 4 with a mating lever 29 of fast idle cam 22 so as to swing the latter counterclo-ckwise and thereby swing crank arrn 19 and choke blade 13 downwardly to an open position (to open choke valve 13 as described below) to facilitate the exhaustion of unburned fuel from the passage 11 and engine cylinder in accordance with customary practice.

A bi-metalic thermostat or temperature responsive spring si) is suitably located in juxaposition with a portion of the engine to sense the temperature thereof and is secured at one end to a stud 31 carried by the engine. A -crank arm 32 pivots on stud 31 and is secured at its outer swinging end to the lower end of a connecting link 33. The upper end ot link 33 is pivotally connected to an arm 34a of a U-shaped lever 34 suitably secured to an extension of choke shaft 14 to pivot therewith. In the present instance the lever 34 is provided with a slot 35 extending radially toward shaft 14 andis tightly clamped to the latter by means of a screw 35 which draws opposite sides of slot 35 toward each other. Keyed to an extension of choke shaft 14 outwardly of crank arm 19 is a choke actuating lever 37 which overlies in FIGURE 4 the clockwise edge of a stop 3S integral with arm 19. Thus upon clockwise swinging of arm 19 in FIGURE 4, stop 3S will engage lever 37 and swing the latter and choke blade 13 clockwise to an open position.

In operation of the device described thus far, the crank arm l19 and fast idle cam 22 are weighted to swing the latter counter-clockwise to a choke open or warm idle position. When the engine is cold, thermostatic spring 30 operates to swing arm 32 counter-clockwise in FIGURE 6 and thereby to swing lever 34 and choke blade 13 counter-clockwise to the closed position with increasing force as the temperature decreases. Conversely, as the temperature operating on spring 30 increases, the counter-clockwise closing force on choke blade 13 decreases. As choke blade 13 and shaft 14 are pivoted counter-clockwise to the cold position by thermostatic spring 30, actuating lever 37 keyed to choke shaft 14 will swing into contact with stop 3S and cause counter-clockwise swinging of pivot arm 19, thereby to elevate link Z0 and swing the fast idle cam 22 clockwise to its co-ld position illustrated in FIGURE 4.

In order to open choke blade 13 to a predetermined position when the engine is idling, a vacuum actuated device is provided comprising a sheet metal housing 3Q, FIGURE 7, containing a iiexible diaphragm 40 securely clamped around its peripheral edge 41 to partition housing 39 into a rst chamber 42 open to the atmosphere and a second or vacuum chamber 43 connected by means of conduit 44 with induction passage 11 at port 44a downstream of the throttle valve 15, FIGURE 5.

A link or plunger 45is suitably secured centrally to diaphragm 4t? and extends upward and leftward therefrom, FIGURE 6. The left or outer end of plunger 45 is provided with a lost motion slot 45 within which rides one end 47a of a connecting link 47. The opposite end 47h of link 47 extends parallel to end 47a and rides in an arcuate slot 4.8 in lever 34 concentric with choke shaft 14. Thus during operation lof the engine under load, the unbalanced choke blade 13 is free to swing clockwise to its fully open position independently of the position of link 47. When the choke blade 13 is closed, the link end 4'7b will be lat the most clockwise edge of slot 48, FIGURE i6, so that upon vacuum operation of links 45 and 47 as described below, lever 34 and choke blade 13 will be swung clockwise against the force ot thermostatic spring 30 to a predetermined partially opened position.

In order to modulate the opening of `the choke blade 13, a spring 49 is connected at one end Sti with the left end of link 45 and is connected at its opposite end at51 with link 4'7. In this regard, the link 47 loops at 47d around spring 49 in FIGURE 6 so that the modulating spring 49 is feasibly arranged in substantially linear alignment with link ends 47a and 47b.

By the arrangement shown, modulating spring 49 urges and 47a against the inner end of movement limiting slot 46 proximate housing 39, FIGURE 6. yWhen the engine is being cranked in a cold condition and choke blade 13 is closed, the low pressure downstream of throttle valve 15 will be nominal and will be insuicient to actuate diaphragm 40 against the tension of spring 49. Also in order to prevent movement of diaphragm 46 from its inactive position shown in FIGURE 7 during cranking, biasing spring 40a is preferably provided between diaphragm 40 and the base of chamber 43. Accordingly pulsating opening movement of the choke blade 13 is avoided during the cranking operation. As soon as the engine is idling however, the low pressure downstream of throttle will be at a maximum and will be transmitted to chamber 43 to urge diaphragm 40 rightward or downward in FIGURE 7 and to pull link 45 inwardly of housing 39. If the engine temperature is sutiiciently cold, the force of thermostatic spring 30 urging the choke valve closed will be sufficient to maintain the latter closed against the tension of spring 49 as the latter is stretched upon the aforesaid inward movement of link 45. Accordingly link end 47a will ride to the top or outer end of slot 46 upon inward movement of link 45. When the outer end of slot 46 engages link end 47a, link 47 will be pulled downward in FIGURE 6 upon the continued rightward movement of diaphragm 40.

The limit of movement of diaphragm 40 known as the kick position is determined by abutment between the base of diaphragm 40 and a shoulder 39a of housing 39. At the kick position, link 47 will have pivoted link 34 and choke blade 13 to a predetermined open position regardless of the engine temperature. Thereafter, as the engine temperature progressively increases, modulating spring 49 will urge link 47 downwardly or inwardly in FIGURE 6, thereby to progressively open choke valve 13 by swinging lever 34 clockwise until Alink end 47a bottoms against the inner end of slot 46.

It is to be noted in the above regard that the modulated opening of choke valve 13 in response to spring 49 is insensitive to variations in the vacuum pressure downstream `of the throttle valve 15. During cranking, the vacuum force downstream of throttle valve 15 will be insuicient to actuate the diaphragm 40. At lower pressures, the diaphragm 40 will move to its limiting or kick position. Thus when the engine is idling and the vacuum force is at a maximum, the diaphragm 40 will be moved to the kick position. Thereafter as the engine load increases and the vacuum force downstream of the throttle decreases, the increased air ow in the induction conduit 11 will be eifective to blow the unbalanced choke blade 13 'beyond the kick position and eventually to the ful-ly open position at high engine loads.

Referring to FIGURE 2, the horizontal line 52 represents the extent of opening of the choke blade angle at the kick position. In one type of engine, this angle of opening is approximately 19 degrees. If it were not for the modulating spring 49, the `thermostatic spring 30 would hold choke blade 13 at the kick position during engine idling until the thermostatic spring relaxed sufficiently with increasing temperature to enable further opening. The thermostatic spring 30 is necessarily comparatively strong in order to maintain the choke closed during engine cranking. n

The angle of choke opening that would be permitted by the thermostatic spring 30 with increasing temperature is indicated by dotted line 53 which intersects line 52 at 54. If the thermostatic spring 30 only were used, it would be necessary for the engine to warm to well over 100 F. before the choke blade would open beyond the kick position.

By virtue of the modulating spring 49, this spring can be adapted to enable continued opening of the choke blade beyond the kick position at a temperature of approximately 24 F. The relationship between the choke blade opening and temperature resulting from modulating spring 49 is indicated by line 55 in FIGURE l2. This line intersects line 53 at point 56, which indicates the point whereat link end 47a bottoms against the inner end of slot 46,

FIGURE 6. Thereafter continued opening of the choke 6 indicated by line 53a comprising an extension of line 53 in FIGURE 2.

In order to facilitate adjustment of the initial tension in spring 49, link 47 is formed from comparatively heavy wire stock and is provided With elbow bends 47C and 47d. By opening Vor closing the one or the other of the loops formed by the elbow bends 47C and 47a', either the initial tension of spring 49 is adjusted or the position of end 47b is adjusted in slot 48 to accommodate the stack-up of tolerances in the various operating linkages, thereby to provide ready means for calibrating the carburetor for any predetermined desired Voperating condition. Also by virtue ofl the alignment of the axis of coil spring 49 with the ends 47a and 47b of link 47, no side loading between these ends and the sides of slots 46 and 4S will result. Ideally, the ends 47a and 47 b would not move transversely of their respective slots even if links 45 and 34 were removed. Accordingly, frictional resistance in the coupling is minimized.

We claim:

1. In a carburetor for an internal combustion engine, an air induction passage,'a choke valve and a throttle valve in `said passage, temperature responsive means for yieldingly urging said choke valve to a closed position with progressively increasing force in response to progressively decreasing temperature, pressure responsive means in communication with the pressure in said passage downstream of said throttle valve and being shiftable to an actuated position in response to said pressure 'during predetermined operation of said engine, means for `opening said choke valve to a predetermined position in opposition to said temperature responsive means upon shift-v ing of said pressure responsive means to said actuated position including connecting means operatively connecting said pressure responsive means and choke valve, and means for yieldingly urging additional opening of said choke valve in opposition to said temperature responsive means upon shifting of said pressure responsive means to said actuated position including resilient means operatively connecting said pressure responsive means and connecting means.

2. In a carburetor for an internal combustion engine, an air induction passage, a choke valve and a throttle valve in said passage, temperature Iresponsive means for yieldingly urging said choke valve with increasing force to a closed position with decreasing temperature, pressure responsive means in communication with the pressure in said passage downstream of said throttle valve and being shift-able to an actuated position when said pressure is at a predetermined pressure below the pressure that exists in said passage during cranking of said engine, means for `opening said choke valve to a predetermined position in opposition to said temperature responsive means upon shifting of said pressure responsive means -to said actuated position including connecting means operatively connecting said pressure responsive means and choke valve, and means for yieldingly urging additional opening of said choke valve in opposition to said temperature responsive means upon shifting of said pressure responsive means to said actuated position including resilient means operatively connecting said pressure responsive means and connecting means.

3. In a carburetor for an internal combustion engine, an air induction passage, a choke valve and a throttle valve in said passage, temperature responsive means for yieldingly urging closing of said choke valve with increasing force -upon decreasing temperature, pressure responsive means in communication with the pressure in said passage downstream of said throttle valve and being shiftable to an actuated position in response to said pressure during predetermined operation of said engine, means for opening said choke valve to a predetermined position in opposition to said temperature responsive means upon shifting of said pressure responsive means to said actuated position including connecting means operatively connecting said pressure responsive means and choke valve, and means for yieldingly urging additional opening of said choke valve in opposition to said temperature responsive means upon shifting of said pressure responsive means to said actuated position including resilient means operatively connecting said pressure responsive means and connecting means, said pressure responsive means having a iirst link shiftable substantially linearly in one direction upon shifting of said pressure responsive means to said actuated position, said first link having a movement limiting slot extending therein substantially parallel to said direction and terminating oppositely from said direction at one end, said connecting means including a second link having a portion movable in said movement limiting slot and engageable with said one end to be shifted in said one direction upon movement of said pressure responsive means to said actuated position, said resilient means interconnecting said rst and second links and being aligned with said slot to urge said second link substantially linearly in said one direction.

4. In the combination according to claim 3, said pressure responsive means including a pressure responsive diaphragm having said first link secured thereto and extending substantially perpendicularly to said slot, and also including a conduit connecting one sideof said diaphragm with said passage at a location downstream of said throttle valve.

5. In a carburetor for an internal combustion engine, an air induction passage, a choke valve and a throttle valve in said passage, temperature responsive means for yieldingly urging said choke valve with increasing force to a closed position; with decreasing temperature, pressure responsive means in communication with the pressure in said passage downstream of said throttle valve and being shiftable to an actuated position in response to said pressure during predetermined operation of said engine, means for opening said choke valve to a predetermined position in opposition to said temperature responsive means upon shitting of said pressure responsive means to said actuated position including connecting means operatively connecting said pressure responsive means and choke valve, and means for yieldingly urging additional opening of said choke valve in opposition to said tem perature responsive means upon shifting of said pressure responsive means to said actuated position including resilient means operatively connecting said pressure responsive means and connecting means, said choke valve comprising an unbalanced buttery blade adapted to be opened in opposition to said temperature responsive means by the air iiow in said passage during operation of said engine at greater than idling speed, said pressure responsive means being cooperable with the air ow in said passage yto open said choke valve at least to said predetermined position during operation of said engine at idle and greater speeds.

6. In the combination according to claim 5, said pressure responsive means having a iirst link shiftable substantially linearly in one direction upon shifting of said pressure responsive means to said actuated position, said first link having a movement limiting slot extending therein substantially parallel to said direction and terminating oppositely from said direction at one end, said connecting means including a second link having a portion movable in said movement limiting slot and engageable with said one end to be shifted in said one direction upon movement of said pressure responsive means to said actuated position, said resilient means interconnecting said iirst and second links and being aligned with said slot to urge said second link substantially linearly in said one direction.

'7. In the combination according to claim 6, said pressure responsive means including a pressure responsive diaphragm having said rst link secured thereto and extending substantially perpendicularly to said slot, and also including a conduit connecting one side of said diaphragm with said passage at a location downstream of said throttle valve.

8. In a carburetor for an internal combustion engine, an air induction passage, a choke valve and a throttle valve in said passage, temperature responsive means for yieldingly urging closing of said choke valve with increasing force upon decreasing temperature, pressure responsive means in communication with the pressure in said passage downstream of said throttle valve and being shiftable to an actuated position in response to said pressure during predetermined operation of said engine, means for opening said choke valve to a predetermined position in opposition to said temperature responsive means upon shifting 0f said pressure responsive means to said actuated position including connecting means operatively connecting said pressure responsive means and choke valve, and means for yieldingly urging additional opening of said choke valve in opposition to said temperature responsive means upon shifting of said pressure responsive means to said actuated position including resilient means operatively connecting said pressure responsive means and connecting means, said pressure responsive means having a first link shiftable substantially linearly in one direction upon shifting of said pressure responsive means to said actuated position, said connecting means including a second link, said connecting means including lost motion means interconnecting said first and second links and including a movement limiting slot in one of said links extending substantially parallel to said direction, said movement limiting means including a portion engageable with an end of said slot to shift said second link in said one direction upon movement of said pressure responsive means to said actuated position, said resilient means interconnecting said first and second links and being aligned with said slot to urge said second link substantially linearly in said one direction.

9. In the combination according to claim 8, said second link comprising comparatively rigid bendable stock having an open loop therein at a location on the choke valve side of the attachment between said second link and said resilient means, said second link being bendable at said loop to adjust the extent of opening of said choke valve at said predetermined position when said pressure responsive means is shifted to said actuated position.

1). In a carburetor for an internal combustion engine, an air induction passage, a choke valve and a throttle valve in said passage, temperature responsive means having a portion operatively connected with said choke valve for moving in unison therewith upon opening of the latter` and for yieldingly urging said choke valve with increasing force to a closed position with decreasing temperature, pressure responsive means in communication with the pressure in said passage downstream of said throttle valve and being responsive to said pressure for shifting to an actuatedposition during predetermined operation of said engine, means for opening said choke valve to a predetermined position in opposition to the force of said temperature responsive means upon shifting of said pressure responsive means to said actuated position including connecting means operatively connecting said pressure responsive means and choke valve, said connecting means having lost motion means for enabling additional opening of said choke valve independently of said pressure actuated means at said actuated position, and means for yieldingly urging said additional opening in opposition to said temperature responsive means including resilient means connecting saidpressure actuated means and connecting means.

11. In a carburetor for an internal combustion engine, an air induction passage, a choke valve and a throttle valve in said passage, temperature responsive means for yieldingly urging said choke valve with increasing force to a closed position with decreasing temperature, pressure responsive means in communication with the pressure in said passage downstream of said throttle valve and being responsive to said pressure for shifting to an actuated position when said pressure vis at a predetermined value below the pressure that exists in said passage during cranking of said engine, means for opening said choke valve to a predetermined position in opposition to the force of said temperature responsive means upon shifting of said pressure responsive means to said actuated position including connecting means operatively connecting said pressure responsive means and choke valve, said connecting means having limited lost motion means for enabling limited movement of said pressure responsive means towards said actuated position independently of said choke valve, and second means for urging opening of said choke valve against the force of said temperature responsive means comprising resilient means operatively connected with said pressure actuated means and choke valve for ltransmitting to the latter the pressure force urging said limited movement of said pressure actuated means.

References Cited by the Examiner UNITED STATES PATENTS 2,149,023 2/ 1939 Kommer.

2,710,604 6/1955 Snyder 261-39 X 2,926,895 3/1960 Seyfarth 261-39 2,979,047 4/ 1961 Rapplean et al 261-39 X 3,167,254 1/1965 Goodyear 261-39 X HARRY B. THORNTON, Primm Examiner.

T. R. MILES, Assistant Examiner. 

1. IN A CARBURETOR FOR AN INTERNAL COMBUSTION ENGINE, AN AIR INDUCTION PASSAGE, A CHOKE VALVE AND A THROTTLE VALVE IN SAID PASSAGE, TEMPERATURE RESPONSIVE MEANS FOR YIELDINGLY URGING SAID CHOKE VALVE TO A CLOSED POSITION WITH PROGRESSIVELY INCREASING FORCE IN RESPONSE TO PROGRESSIVELY DECREASING TEMPERATURE, PRESSURE RESPONSIVE MEANS IN COMMUNICATION WITH THE PRESSURE IN SAID PASSAGE DOWNSTREAM OF SAID THROTTLE VALVE AND BEING SHIFTABLE TO AN ACTUATED POSITION IN RESPONSE TO SAID PRESSURE DURING PREDETERMINED OPERATION OF SAID ENGINE, MEANS FOR OPENING SAID CHOKE VALVE TO A PREDETERMINED POSITION IN OPPOSITION TO SAID TEMPERATURE RESPONSIVE MEANS UPON SHIFTING OF SAID PRESSURE RESPONSIVE MEANS TO SAID ACTUATED POSITION INCLUDING CONNECTING MEANS OPERATIVELY CONNECTING SAID PRESSURE RESPONSIVE MEANS AND CHOKE VALVE, AND MEANS FOR YIELDINGLY URING ADDITIONAL OPENING OF SAID CHOKE VALVE IN OPPOSITION TO SAID TEMPERATURE RESPONSIVE MEANS UPON SHIFTING OF SAID PRESSURE RESPONSIVE MEANS TO SAID ACTUATED POSITION INCLUDING RESILIENT MEANS OPERATIVELY CONNECTING SAID PRESSURE RESPONSIVE MEANS AND CONNECTING MEANS. 